a-134974 and Pain

Extracellular levels of adenosine (ADO) can be raised through inhibition of adenosine kinase (AK), a primary metabolic enzyme for ADO. AK inhibitors have shown antinociceptive activity in a variety of animal models of nociception. The present study investigated the antinociceptive actions of a novel and selective AK inhibitor, A-134974 (IC(50)=60 pM), in a rat model of neuropathic pain (ligations of the L5/L6 spinal nerves) and explored the relative contributions of supraspinal, spinal and peripheral sites to the actions of A-134974. Systemic A-134974 dose-dependently reduced tactile allodynia (ED(50)=5 micromol/kg, i.p.) for up to 2 h. Fall latencies in the rotorod test of motor coordination were unaffected by systemic administration of A-134974 (at doses up to 30 micromol/kg, i.p.). Administration of A-134974 intrathecally (i.t.) was more potent (ED(50)=10 nmol) in relieving tactile allodynia than delivering the compound by intracerebroventricular (ED(50)>100 nmol, i.c.v.) or intraplantar (ED(50)>500 nmol) routes suggesting that spinal sites of action are the primary contributors to the anti-allodynic action of A-134974. The anti-allodynic effects of systemic A-134974 (10 micromol/kg, i.p.) were antagonized by the non-selective ADO receptor antagonist, theophylline (30-500 nmol) administered i.t. These data demonstrate that the novel AK inhibitor A-134974 potently reduces tactile allodynia through interactions with spinal sites and adds to the growing evidence that AK inhibitors may be useful as analgesic agents in a broad spectrum of pain states.

Topics: Adenosine Kinase; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Hyperalgesia; Male; Nerve Crush; Nociceptors; Nucleosides; Pain; Pain Measurement; Peripheral Nervous System Diseases; Phosphodiesterase Inhibitors; Physical Stimulation; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Theophylline